Remove SyncService and introduce context-based offline mode and state management

- Delete `SyncService` and its associated bidirectional synchronization logic.
- Add multiple context providers (`OfflineProvider`, `AlertProvider`, `LangContext`, `UserContext`, `SessionContext`, `WorldContext`, `SettingBookContext`) for contextual state management.
- Implement `SecureStorage` for OS-level secure data encryption and replace dependency on `SyncService` synchronization.
- Update localization files (`en.json`, `fr.json`) with offline mode and error-related strings.

context/EditorContext.ts

@@ -0,0 +1,10 @@
+import {createContext} from "react";
+import {Editor} from "@tiptap/core";
+
+export interface EditorContextProps {
+    editor: Editor | null
+}
+
+export const EditorContext = createContext<EditorContextProps>({
+    editor: null
+});